Forums > Land Yacht Sailing Construction

Wheel base length to width ratio?

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Created by prairiepilot 4 months ago, 9 Feb 2018
prairiepilot
24 posts
9 Feb 2018 9:40AM
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Hi all, I'm back building another sailer. I'm loosely following drawings I found on this forum but still have a question on how wide to make the rear axle. Front axle to rear axle is 69" so how wide should the wheel base be? Is there a magic ratio or does it not matter much on a freestyle yacht like this? BTW; getting that front steering fork aligned was a major pain. After welding, cutting, welding,cutting and welding again I think I got it close. Any hints? Thanks!


Gizmo
SA, 2834 posts
9 Feb 2018 1:38PM
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If you are making it to fit class specs (and I would suggest you do) to maintain some ability to race against other yachts at some stage or perhaps the next owner might.
Depending on where in the world you are will depend on your local class spec., but there is a world wide class called International 5.6 which would seem to match your pictures.
The I5.6 has now been broken down to 2 sub classes, a SPIRIT version (basic type of yacht) and the SPORT version (unlimited aerodynamics and design features).

The 5.6 class is based around the yacht being able to fit within a rope loop of 5.6m , the length / width ratio is open. So back to your original question 'what is best'

Lets start with width, ideally you should be able to touch both wheels and use the yacht a bit like a wheelchair to get off a start line., then work from there.

prairiepilot
24 posts
9 Feb 2018 12:20PM
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I'm in North Dakota USA. There probably isn't another sail cart within 500 miles of me. I'll just be sailing around parking lots and empty fields all by myself. I'm just looking to make an easy to sail rig that maybe my wife can try.

Gizmo
SA, 2834 posts
9 Feb 2018 8:27PM
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Rather than re-designing a yacht just build to an already proven set of plans.... These plans have been developed with hundreds of yachts good parts designed in and the bad out.....

www.seabreeze.com.au/forums/Land-Yacht-Sailing/Construction/Lake-Lefroy-Mini-Plans--

seabrit2
37 posts
10 Feb 2018 6:01AM
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Totally agree, cut your teeth on building a lefroy. The build is quick !! Then once you know what you like / dislike, come up with your own design. The build will be ALOT longer !!

Gizmo
SA, 2834 posts
10 Feb 2018 9:43AM
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Just a couple of points from your first pics, square tube is not ideal for the main spinal tube as it will twist far more than a round tube.
Careful of the stub axles, welded like that will possibly fracture the weld due to the twisting action.

Hiko
1180 posts
10 Feb 2018 9:24AM
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58 inches width to the outside of the rear tyres would be a good width
and should enable you to reach the tyres to move the yacht
That measurement would make the yacht very close to the mini
5.6 rope measurement rule which is well proven.
Agree with the comments above regarding square tube spine and offset stub axles Turning the axles 90 degrees may help.

seabrit2
37 posts
12 Feb 2018 2:48AM
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I agree with gizmo, a square spine is not the perfect material from a tortion to weight ratio. However, I built my first yacht to lefroy plans using a square spine, worked fine. If you are racing and want to keep the weight to a minimum and have the spine wind up under load to preserve a little extra energy, go for round. For a first yacht, the main think is get the thing finished and rolling, have fun, then you will be hooked and have the enthusiasm to build something more complex.

prairiepilot
24 posts
18 Feb 2018 9:14AM
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I took your advice. Started over and used round tube for the spine. Also had better luck welding up the steering unit this time.






KAONAONA
229 posts
23 Feb 2018 4:39AM
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You might think about laying the seat down a lot more unless you are planning on sheeting from the back. Get some seat belt tabs welded on too! Although not needed in wide open areas, some kind of brake would be good for the parking lots and fields you plan to sail. A simple scrub brake will do. Any sort of foot pan or small floor area is suggested also.

prairiepilot
24 posts
23 Feb 2018 9:51AM
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Kaonaona, I plan on sheeting from behind the seat. I'm having the seat upright cuz I broke my neck last summer and sitting up feels better then lying back and having to crank my neck forward.

I've been struggling to get any of my sails to work with the 2 masts I have. Everything is old and does not match. Cheap masts and sails are hard to come by in my part of the world. I want to try using an uncut sail if possible but also bought an old sewing machine to try to modify some sails as well. I built my mast step according to the Lefroy plan but also made an insert so I can hopefully use an uncut sail with preset downhaul and it will rotate freely.
-For internal support I have a 1.5" x 48"/121cm long steel tube ( 3mm walls) which fits snugly into a length of ABS pipe which fits snug in the mast step. The upper portion of ABS pipe fits perfectly into my two masts. It goes about 85 cm into the masts. the mast should rotate freely I'm hoping.



I want to set the downhaul using the bracket on the rotating mast support for uncut sails but will probably attach the downhaul to the frame like on the Lefroy plans for sails that I modify.






I still have to reinforce the mast step.
Any thoughts?

Chook2
WA, 1198 posts
23 Feb 2018 5:12PM
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Nice work.
Here is an old phone photo, so sorry about the clarity.
A standard 10 degree LLMini Step with 25mm x 3mm Flat bar added. Yacht build number 8 of mine.
Don't weld it all the way round.

Your yacht looks to be around 5 degrees of rake, which is much better? All my later mini's were changed to only 3 degrees of rake to take uncut windsurfer sails.


prairiepilot
24 posts
24 Feb 2018 8:30AM
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I'm getting closer. Just need the snow and ice to go away.




seabrit2
37 posts
25 Feb 2018 12:56AM
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The key to uncut sails is huge downhaul !! 6:1 pulley system or I find a ratchet strap works better and cheaper. If your lower eye on your mast support tube does not work, no worries, attaching to the mast step does restrict weather cocking but still works great. There is a huge moment on the sail by the wind and twists off fine

prairiepilot
24 posts
25 Feb 2018 1:28AM
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i found this pulley set. Is this considered 6:1 with the 6 pulley wheels?



Windcrazy
86 posts
25 Feb 2018 6:07AM
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Don't forget good wheel bearings, cheap ones can't handle the side load for very long.

seabrit2
37 posts
25 Feb 2018 11:01AM
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Yes that will work, I suggest a thicker rope since you will sit in the yacht and pull as hard as you can !! Hopefully the hooks do not straighten in you

Test pilot 1
WA, 1425 posts
26 Feb 2018 8:34AM
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Select to expand quote
seabrit2 said..
Yes that will work, I suggest a thicker rope since you will sit in the yacht and pull as hard as you can !! Hopefully the hooks do not straighten in you


And a better quality rope as the cheaper ropes dont have a twisted core and absorb grit which tends to chew the rope apart from the inside :- result is sudden failure!

Chook2
WA, 1198 posts
26 Feb 2018 8:54PM
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I agree about a good rope if your sailing for long periods (and friends are not dragging your expensive sheet along the surface when they borrow your craft.)

This was Greg's suggestion to modify my rope and ease my carpal tunnel problem with my hands after long periods sailing.

I reduced my 12mm dyneema sheet rope down to it's core at the rear of my yacht to lighten the pressure needed to roll it round all the blocks. It works a treat too.

In the top pic you can see the splice (change of colour) on the rear rope and the frayed area on the full 12mm diameter is from continued use through the ratchet block at the front. Fully sheeted hard the beginning of the splice is almost into the ratchet block towards the front of the boom.
Next pic, you can see a bit of a tuft emerging from my splice just entering the top rear block. I need to be neater "taper splicing" it next time.
See how soft and pliable the core is hanging there over the bottom rear block (compared to the 12mm through the block ahead of it).
I'm stationary here, just starting to sheet in before I move off.

For a "fid", I modified a 10mm hollow aluminium knitting needle and it worked a treat for splicing the rope.


I just stitched the join (with "doubled up" denim cotton thread) at the 5.20 point of this video, so it threaded through the last block easily when sheeting in.

I've run this modified 12mm Dyneema rope for over 3 months now and there is a lot less effort to pull the sheet rope, as the thin dyneema core is so soft running around the rear blocks.
It's still 12mm through the ratchet block and where I handle it (with the cheap dimpled palm Bunnings gardening gloves so a death grip isn't required to retain the rope)


Don't get the ones below (as they grip TOO WELL and wont release the rope easily even when you completely relax you fingers). Don't ask me how badly I crashed!!!!



Hiko
1180 posts
27 Feb 2018 1:45AM
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Had to smile Chook about "friends dragging your expensive sheet rope" !
A common frustration !
Great info and tutorial yet again Chook Thanks for posting.

kennatt
25 posts
27 Feb 2018 4:56PM
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www.bing.com/images/search?q=windsurfing+pully+hooks&id=3A086DD2958EAB60EEC5449619BFA40C86A7CC05&FORM=IQFRBA
see above its what most windurfers use. Buy two one on sail and other fixed to base . Some have a cleating system as well buy downhaul rope from same store thin dynema is the norm basically unbreakable.,I have my yacht rigged with a cut down windsurf mast extension using the pully system from it,bolted to the frame and a four roller pulley hook to the sail,the base has four pullys and a cleat so can adjust on the fly.No means of uploading photos but if you again search windsurfing mast extensions you will see the pully system at the bottom of the extension.Cut top tube off and used base as above.



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"Wheel base length to width ratio?" started by prairiepilot